Method of bypassing a pipeline in a multiple pipeline system

Abstract

The present invention relates to an apparatus and method of producing gaseous and liquid component streams from at least two multi-phase streams in at least two pipelines, the method comprising at least the steps of: (a) passing a first multi-phase stream along a first pipeline and through a first slugcatcher system; (b) passing a second multi-phase stream through a second pipeline and a second slugcatcher system; (c) passing a first pig down the first pipeline to create a first pig-slug mass in the first pipeline; and (d) passing at least a fraction of the first multi-phase stream upstream of the first pig-slug mass to the second pipeline along a crossover line.

What is claimed is: 
     
       1. A method of accommodating a pig-slug mass in a first pipeline upstream of a first slugcatcher system comprising the steps of:
 (a) passing a first multi-phase stream along, a first pipeline and through a first slugcatcher system arranged to provide a first gaseous component stream and at least one first liquid component stream: 
 (b) passing a second multi-phase stream through a second pipeline and a second slugcatcher system arranged to provide a second gaseous component stream and at least one second liquid component stream; 
 (c) passing a first pig down the first pipeline to create a first pig-slug mass in the first pipeline; 
 (d) passing at least a fraction of the first multi-phase stream upstream of the first pig-slug mass to the second pipeline along a crossover line; and 
 (e) selectively combining the first gaseous component stream and the second gaseous component stream downstream of the first and second slugcatcher systems; 
 (f) treating one or both of the first and second gaseous component streams to provide one or more gaseous component streams selected from the group consisting of natural gas liquids, natural gas and LNG, the treating comprising:
 (i) passing one or both of the first and second gaseous component streams to an NGL recovery system to provide an NGL stream and a methane-enriched overhead stream; 
 (ii) compressing the methane-enriched overhead stream in one or more compressors to provide a methane-compressed stream; 
 (iii) liquefying the methane-compressed stream in a liquefaction system to provide a first liquefied stream; 
 (iv) expanding the first liquefied stream in an expansion device to provide a final mixed-phase stream; and 
 (v) separating the final mixed-phase stream in an end gas/liquid separator to provide a LNG stream, and an end gaseous stream. 
 
 
     
     
       2. A method as claimed in  claim 1  wherein the crossover line is opened when the first pig is downstream of the crossover line. 
     
     
       3. A method as claimed in  claim 1  wherein the first pipeline comprises a first pig signaller between the crossover line and the first slugcatcher system, and the crossover line is opened when the first pig signaller detects the first pig. 
     
     
       4. A method as claimed in  claim 1 , wherein the volume of the first pipeline between the crossover line and the first slugcatcher system is the same or greater than the volume of the first pig-slug mass in the first pipeline. 
     
     
       5. A method as claimed in  claim 1 , wherein the total volume of the first pipeline between the crossover line and the first slugcatcher system plus the volume of the first slugcatcher system is the same or greater than the total volume of the first pig plus the first pig-slug mass. 
     
     
       6. A method as claimed in  claim 1 , wherein the volume of the first pipeline between the crossover line and the first slugcatcher system is the same or greater than the total volume of the first pig plus the first pig-slug mass. 
     
     
       7. A method as claimed in claim l further comprising the steps of:
 (g) selectively opening the crossover line between the first pipeline and the second pipeline upstream of the first and second slugcatcher systems to pass at least a fraction of the first multi-phase stream through the second pipeline and the second slugcatcher system; and 
 (h) reducing, the flow of the first multi-phase stream along the first pipeline downstream of the crossover line during step(g). 
 
     
     
       8. A method as claimed in  claim 1  wherein the crossover pipeline selectively passes all of the first multi-phase stream from the first pipeline to the second pipeline. 
     
     
       9. An apparatus for accommodating a pig-slug mass in a first pipeline upstream of a first slugcatcher system, comprising:
 (a) a first pipeline and downstream first slugcatcher system for passing a first multi-phase stream along the first pipeline and through the first slugcatcher system arranged to provide a first gaseous component stream and at least one first liquid component stream; 
 (b) a second pipeline and downstream second slugcatcher system for passing the second multi-phase stream through the second pipeline and the second slugcatcher system arranged to provide a second gaseous component stream and at least one second liquid component stream; 
 (c) a first pig launcher for passing a first pig down the first pipeline to create a first pig-slug mass in the first pipeline; 
 (d) a crossover line connecting the first pipeline and the second pipeline for passing at least a fraction of the first multi-phase stream upstream of the first pig-slug mass to the second pipeline; 
 (e) a junction and/or a gaseous stream crossover line for selectively combining the first gaseous component stream and the second gaseous component stream downstream of the first and second slugcatcher systems; and 
 (f) a processing facility for treating one or both of the first and second gaseous component streams to provide one or more gaseous component streams selected from the group consisting of natural gas liquids, natural gas and LNG, the processing facility comprising;
 (i) an NGL recovery system to provide an NGL stream and a methane-enriched overhead stream from one or both of the first and second gaseous component streams; 
 (ii) one or more compressors to compress the methane-enriched overhead stream to provide a methane-compressed stream; 
 (iii) a liquefaction system to liquefy the methane-compressed stream to provide a first liquefied stream; 
 (iv) an expansion device to expand the first liquefied stream to provide a final mixed-phase stream; and 
 (v) an end gas/liquid separator to separate the final mixed-phase stream to provide a LNG stream and an end gaseous stream. 
 
 
     
     
       10. The apparatus as claimed in  claim 9  wherein the first pipeline comprises a first pig signaller between the crossover line and the first slugcatcher system. 
     
     
       11. The apparatus as claimed in  claim 9  wherein the volume of the first pipeline between the crossover line and the first slugcatcher system is the same or greater than the volume of the first pig-slug mass in the first pipeline. 
     
     
       12. The apparatus as claimed in  claim 9 , wherein the total volume of the first pipeline between the crossover line and the first slugcatcher system plus the volume of the first slugcatcher system is the same or greater than the total volume of the first pig plus the first pig-slug mass.